Within 31 days after definitive surgery, all patients begin therapy. Patients undergo radiation therapy with doses according to their Arm randomization on days 1-5, 8-12, 15-19, 22-26, 29-33, 36-40, and 43-47 (weeks 0-6). All patients receive vincristine intravenously (IV) over 1 minute (or infusion via minibag as per institutional policy) on days 8, 15, 22, 29, 36, and 43 (weeks 1-6).